Inside Out: Immune System
by MCV4
Summary: How might real-world sicknesses and infections translate to the world of Inside Out? - When Riley comes down with a severe case of meningitis, the Emotions come face-to-face with the invisible war of the microbes for the first time.


_Welcome to Inside Out: Immune System! Having just taken an immunology class, and then seeing those spectacular views of Riley's mind in the movie, I was inspired with a vision of my favorite aspect of biology rendered in the same awesomely beautiful cartoon style._ _In this story I attempt to translate a real-life illness into the fantasy world of Inside Out - while maintaining scientific accuracy where possible._

 _This story is set 7 years after the movie. Though Riley did adjust to San Francisco, she ultimately decided to return to Minnesota for college, where she is reunited with her best friend Meg. With her parents still living in California, it's Riley's first time living in dorms on campus… and her first time being sick away from home._

* * *

Three months into her freshman year at the University of Minnesota, on a Friday like every other one that semester, Riley woke up to the sound of her alarm clock, getting ready for the early morning lecture class she shared with her roommate and best friend Meg.

Inside Riley's head, the emotions dashed to their seats at the control panel. Joy drove as she usually did each morning, recalling up a few happy memories of Meg for the projector at just the moment when Riley gazed upon her friend's sleeping form across the room, then expertly moving her joystick to get Riley out of bed and into her morning routine. Disgust added a few touches at her console, making Riley absent-mindedly run her fingers through her tangled and knotted hair.

But something was wrong today. Meg didn't stir. Riley climbed down from her bunk bed and brushed her hair in front of the mirror as she spoke loudly across the room. "Meg, time to get up!" No response.

Inside Riley's head, the emotions glanced across their large shared control panel. After many years together they could often coordinate without even a word. By silent mutual agreement, Joy and Disgust both let go of their controls, while Fear pushed some buttons on his section of the console.

"Meg, are you okay?"

"I don't feel well," came the muffled reply. "Go on without me."

Naturally, Riley's first reaction was to skip their shared morning class and try to take care of her friend. But Meg refused. "Go to class and take notes for me!"

At lunchtime Riley called Meg to check on her. They'd had plans to attend a party just off campus that evening, but it seemed Meg wasn't going to make it. Later that afternoon Meg's parents came by to take her home for the weekend, promising to make her better with some nice hot chicken soup.

Riley went to the party by herself, but being hit on by increasingly drunk young men as the night proceeded wasn't nearly as fun without Meg there to laugh at her reaction. With Disgust piloting, she left early and turned in for the night.

Sadness had dream duty that night, but as usual, dozed off partway through.

The next morning, in her little room in Headquarters, Joy woke up to damp sheets and an uncomfortably warm room. Throwing off her covers, she skipped out into the main control room, running into the familiar voices of her fellow emotions.

"Does anyone else think it's hot in here?" Disgust complained loudly, fanning herself as she emerged into the main control room.

"Yeah, what is going on?" mumbled Sadness sleepily from her seat.

Anger sat on the couch holding a newspaper with the headline "Heat Wave! Record Highs in Riley's Mind Today."

"Please don't let Riley be sick again," whined Fear. "Oh no, we're sick! Help, we're all gonna die!" Fear started running around in his usual hysterics.

Out in the real world, Riley was sluggish and fatigued as she dragged herself through her morning routine. She wasn't feeling her usual chipper self today. She began to become concerned that she'd come down with something, either from Meg or from someone at that frat party last night…

"Good thing today's a Saturday," said Joy, reading the thought into Riley's active consciousness. Disgust let go of her controls, stopping Riley mid-motion in front of the mirror. The others took over and piloted Riley back to bed. She would sleep in today.

Riley's eyes closed as she drifted off, and the great viewscreen in Headquarters shut off. But the emotions were furiously debating what to do about the sweltering temperatures.

"Guys, this is hotter than we've ever been. I think Riley needs a thermometer to see how high her fever is!"

"Oh, don't worry. I'm sure it's just another flu."

"I knew we should've gotten that flu shot the other day!"

Most of the argument was between Joy and Fear, and while they argued, Sadness wandered away from the console and started walking around searching for a cooler spot to sit. And that's when she encountered the creature.

A small pink gremlin on the carpet near the entrance to the Train of Thought's Headquarters station, taking bites out of the floor, munching on the carpet and chirping merrily. A trail of destruction leading in from the open doorway.

Joy stopped and turned around when Sadness called out. "Uh, guys? I think I found something."

Joy squealed in delight at the new arrival. "Aww, he's so cute!" She excitedly skipped over to the gremlin and knelt down. "Hey, little buddy. Who are you?"

The pink creature started to look up, but even as it did, revealing beaded eyes and a sinister smile full of small sharp teeth, the creature suddenly expanded and then split down the middle – and now two identical creatures, pink ovals with faces and tiny stringy limbs, stared back.

One of the creatures crawled forward on its sphagetti-like legs, reaching two of them out like arms to hold onto Joy's outstretched hand. The creature attached with its legs, pulling itself up. Its outer surface was coated in some sort of transparent slime; only its thin legs could be easily grasped.

And then, without warning, the creature opened its mouth and bit down into the flesh of Joy's wrist.

"OW!"

Joy reflexively withdrew her hand and then shook it, both in pain and in an effort to shake off the creature, which finally fell to the ground and rolled onto its back, still smiling up at Joy and chirping merrily, as it munched happily on the piece of Joy's arm it had just bitten off.

"Joy!" Fear scuttled up to her side and grabbed her arm, inspecting the bite which was now 'bleeding' golden energy essence.

"YOU!" Anger stepped up, enraged at the strange creature that had just hurt his friend. With his head shooting up flame, Anger strode right up to the chirping creature and slammed his fist down.

The creature squealed in pain at the impact, but because of its slippery, slimy skin, the creature was easily squeezed out of the way by Anger's fist, rather than being crushed against the floor. The creature skidded off to the side, wailing and crying like a toddler.

When the emotions looked up, they saw not just the two little critters who were there before. There were now six of the slimy pink critters with noodle-like legs… four of which were chewing up the carpet around the entrance leading to the Train of Thought, and the other two of whom were now staring at the Emotions with menacing smiles on their faces.

"I know what these are," Sadness suddenly piped up, realizing she remembered seeing pictures of them in one of Riley's high school biology textbooks. "They're bacteria!"

"Don't bacteria – " Fear squeaked out.

" – make you sick!" Disgust finished.

"Only certain kinds of bacteria," Sadness mumbled, now remembering more from Riley's old lessons.

"I bet this kind does," growled Anger.

The emotions all warily backed away from the bacteria, while the two that they'd apparently offended earlier began to advance towards them. Most of the bacteria, however, were merrily and obliviously chewing up whatever they touched – and were multiplying before their eyes, too. There were now no less than twelve of the pink creatures crawling about on the ground, some of which had eaten through the carpet and were now digging into the metallic floor beneath, ripping out small chunks with their teeth and eating them with great zest.

"Hold it!" boomed a voice from above, and before the Emotions could react, something suddenly fell from the high ceiling onto the floor, plopping right between the Emotions and the invading Bacteria like a big wall of gelatin. The gelatin then moved and it looked like a giant white translucent centipede or worm of some kind; it had a long cylindrical body with many pairs of small stubby legs supporting it. On one end of the body there was an elderly, wizened face, and two arms sticking out on either side. A long lumpy rod of bluish material embedded inside the body was evidently the nucleus of this particular cell.

The new arrival turned towards the little pink Bacteria, reared up onto its hind legs, and reached out with both hands, grabbing ahold of the creature and lifting him up. The creature squealed and struggled, but the great white worm had a firm grasp. The worm pulled the squirming pink gremlin back towards its face and then shoved the creature right into its mouth. The Bacteria screamed as it dissolved into the giant worm's body.

The white worm crawled forward and threw its arms forward, reaching for the other Bacteria, but the slimy little gremlin slipped free and fled to the safety of its companions, squealing unhappily.

The worm turned back to face the five Emotions who were standing frozen in shock, watching the scene unfold.

"Hi guys!" the worm said, extending its stretchy white hand out to shake hands. "I'm Mike, your resident security guard!" He reached into his underside and pulled a blue police badge out of himself, flashing it. "An honor to serve you."

"Uh…" Joy hesitated for a moment, but shook it off and extended her hand. "Thanks for the help! I'm Joy."

"I'm Anger!"

"Disgust."

"Sadness."

"Fear."

Mike shook hands with each Emotion in turn.

"Sorry to be rude here," said Disgust, "but what are you?"

Mike smiled a grandfatherly smile. "I'm a White Blood Cell! We protect Riley from invaders that make her sick!"

Mike lumbered towards the growing crowd of glistening pink Bacteria. Rearing up on his hind legs he extended several more pairs of 'arms' from his body, grabbing in several directions at once. The ones toward the back of the crowd seemed wholly absorbed in the pleasures of munching on the physical structure of Headquarters, but those closer to the front started to look up in fear and scamper away, bumping into their comrades as they fled from the towering White Blood Cell. But one after another Mike's arms caught up to each of the critters; some managed to escape, but Mike's arms slithered and fanned through the area in front of him, bringing a steady stream of wiggling, squealing Bacteria up to his mouth. Those who failed to slip from his grasp were devoured in a seemingly continuous procession.

But it wasn't enough – despite Mike's valiant gustatory efforts, the crowd of Bacteria only seemed to get bigger, denser, louder, and even began to pile up in the middle, forming a shallow mound of writhing pink creatures. "Hungry!" they seemed to cry out, spreading over the floor, climbing up the walls, chewing away at the structure of Headquarters itself. What was formerly the rectangular door leading to the Train of Thought's rails had now become a huge, jagged hole in the wall, with Bacteria chewing on its edge, expanding it ever larger.

Then, suddenly, a series of explosions rocked the area, and clouds of effervescent purple gas spread through the area. All the Emotions made varying faces as the noxious, unpleasant smell drifted across the room. But at the same time the chattering of the Bacteria became almost immediately replaced by desperate screams as the gas seemed to burn through their pink skins, causing random dark spots to appear on their surfaces. Seemingly dozens of the pink critters all at once began to swell up and shriek in pain as they became enveloped in the gas and their noodly arms fell off and black burn marks appeared all over their bodies – and then, like popcorn popping, they began to burst, leaving only some sticky, steaming blackened goo where they had once been.

Under the influence of gravity, much of the goo seemed to end up in the large pit that had formed where the Bacteria ate their way into the floor, creating a big "pond" of oily black residue. Only a few Bacteria on the edges of the crowd had survived, having been far enough from the explosions and not been fully burned. Most of them lay on their backs, next to the small puddles of black goo that had once been their brothers. Some were silent, others whining or whimpering in pain; all of them had various apparent injuries to parts of their bodies.

Mike seemed wholly unaffected by what had just happened, reaching out and grabbing one of the injured Bacteria that lay in his path. The creature gave a choked whimper, offering little resistance as Mike shoved it into his mouth, in stark contrast to the vigorous efforts with which all the uninjured Bacteria had tried to escape Mike's grasp previously.

"YEAH!" Anger cheered at the demise of the Bacterial critters. Joy whooped and applauded, spinning around exuberantly. Fear let out a very big sigh of relief.

Then Mike lowered himself to the floor and crawled forward, through the huge mess of debris and dead or injured critters, licking the floor as he went, slurping everything up. "Eww!" Disgust almost yelled, hurriedly turning around and falling to her hands and knees as she tried not to vomit. The other Emotions looked on in shock, all silently agreeing with Disgust's loudly verbalized sentiment. Within the span of a second they each decided to turn around as well, to pay more attention to their nauseated friend rather than to Mike's highly unappetizing clean-up.

Due to having their backs turned, the Emotions did not see another White Blood Cell rolling up to them from behind and extending two 'hands' out of his body.

"Hi guys! I'm Phil."

The startled Emotions turned around again.

Phil was a round, very translucent white-purplish blob with a tri-lobed blue nucleus. Unlike Mike, Phil's cytoplasm seemed to be largely filled with little round sacks of effervescent purple material – evidently the source of the poison gas from earlier.

"Thank you so much for saving us!" said Joy excitedly, shaking Phil's stubby hand. "I'm Joy!"

"Disgust, Anger, Sadness, Fear," said Disgust in a much less excited voice, pointing to herself and then her fellow Emotions in turn. "And, uh, yeah, thank you." Across the room Mike was still slurping at the toxic goo left over from the battle, and the sounds were quiet but still audible where the Emotions stood.

"You're welcome," said Phil, "but don't thank me yet. I saw a bunch more of those Bacteria on my way in here, this one might take a little while to clean up."

"M-m-more?" squeaked Fear.

"Yeah, pretty far below us though. Hopefully the fight won't come all the way back up here again."

They were interrupted by the sounds of more Bacteria chirping. Fear went pale again and the others immediately started looking around. It was soon evident that a few of the injured Bacteria scattered around the room had recovered from their injuries. They were back on their noodle-like 'feet' and once again gleefully eating at the carpet under them as if nothing had happened.

"Hold on, let me take care of those guys," Phil said quickly, and then he began to half-roll, half-ooze across the room. He lowered his mouth right onto one Bacteria; the little Bacteria turned and tried to flee, only to be trapped by Phil's hands coming down on the other side, boxing it in. The squirming critter vanished into Phil's mouth, kicking and screaming.

Phil rushed from one Bacteria to the next, chasing and eating them. Some of them had divided by the time Phil reached them, but just like Mike, Phil had the ability to grow extra arms to grab onto more than one Bacteria at the same time. Each group of two or four Bacteria stood no chance against the White Blood Cell, and although some managed to slip out of Phil's grasp a few times, they were all ultimately captured by Phil's relentless pursuit, and eaten by him. A few of the Bacteria fled right into the large pit from the earlier infestation, but Mike was right there to stop them.

"You guys are awesome!" gushed Joy.

By this point Mike had sucked up almost all of the toxic goo from the dead Bacteria, and some black spots had appeared throughout his large body, the undigestable leftovers from his unhealthy meal. With the toxic black pond gone, the damaged floor underneath was revealed. Almost the entire floor of Headquarters from the train station door all the way up to the back of Sadness's right-side seat at the console had been scraped bare. Most of the floor itself was ruined too, occupied by a large pit of jagged metal and concrete edges with a few sparking wires and pipes exposed in random spots. Mike crawled over to the large hole in the exterior wall where the door had once been and stuck his head into the train platform area. "Where's the repair team?" he hollered.

Mike withdrew back into the room and came back to stand with Phil and the Emotions. Shortly afterwards, two Mind Workers came in wearing hard hats and tool belts, dragging a cart full of steel planks and rivets behind them. Both of them saluted to the Emotions and the two White Blood Cells. "Astrocyte Team 1-4 at your service!"

"Thanks guys!" said Joy, while the two Workers hopped down the edges of the pit on the floor and began the repairing.

* * *

Riley woke up from her nap feeling no better than before. In fact, she now had a headache, and the light from the edges of the window curtains was bothering her.

The warning lights on Fear's section of the console were blinking. "Riley's got a headache!" shouted Fear across the room. "Light makes it worse, close the curtains!"

Joy steered Riley's head up off the pillow to get a better look towards the window, and more of Fear's pain display lit up. "The curtain's already closed!" she called back.

"And that move just made her neck hurt, too!" Fear said.

"Ugh, what is going on?" Disgust asked.

"Must be from all that damage the Bacteria did," Joy speculated. "I'm sure it'll all go away as soon as they finish fixing it."

"How long is it going to take? We're in pain here!" said Fear. "And – and – " he started hyperventilating – "it's not getting any better!"

A moment of silence.

"What do we do, what do we do, we have to help Riley!" Fear started babbling, unable to take the silence.

"We'll be just fine," Joy reassured, ever optimistic. "Do we have any pain pills? Tylenol, aspirin, anything?"

She punched the query into their console. The answer from Long Term Memory was the opposite of what they wanted. "NOPE!" Anger shouted angrily. "Why didn't we think of that 3 months ago and brought some from home?"

"And we're in no condition to go out and buy any!" Fear whined.

"Riley's been hurt worse before," Joy said, pulling up a memory of a broken arm from a collision during a hockey game several years ago. "We'll just tough it out."

"Not in her head though!" Fear argued. "This might be something serious! Like E-Ebola or something!"

"What if we call Mom and Dad?" Sadness suggested. "They usually know what to do."

"Great idea!" said Joy. "Fear, help me drive!"

Joy and Fear both worked their consoles. In the real world, Riley lay on her bed with her eyes closed, as her hands fumbled around searching for her cellphone.

"Aha!" Joy said as she piloted Riley's fingers closed around the phone.

"The light from the phone is going to hurt," Fear said.

"No way around that," Joy replied. "On the count of three…"

In the real world, Riley steeled herself for a moment and then opened her eyes, ignoring the glare from her phone's screen long enough to quickly pull up the "recents" and select Mom's number at the top. She closed her eyes again and put the phone to her ear.

The Emotions listened to the rings of the phone in Riley's ear and eagerly anticipated Mom's voice.

But the sound they heard instead was some indistinct shouting from Phil and Mike behind them, followed by the familiar shrieks of Bacteria, and then a cry of terror from one of the Mind Workers who had been doing repairs.

"Riley, dear?" Mom's soothing voice sounded over the intercom a moment later, but the Emotions barely noticed. They were all swiveled around, looking on in horror as the Mind Workers backed away from a spot in the repair pit where two bacteria, then four, then a torrent of them, burst out from the ground like a geyser.

Mike had positioned himself along the gap in Headquarters' wall, seizing any Bacteria that tried to slip in, while Phil rushed to aid the Mind Workers. He plunged right into the crowd of bacteria that were rapidly filling the pit, grabbing the critters all around him and stuffing them into his mouth nonstop. The dying screams of the bacteria filled Headquarters.

But he was too late to save the Mind Workers, whose screams were covered by those of the Bacteria as they latched on to the Mind Workers' pudgy blue bodies from all directions and savagely bit off chunks of cytoplasmic flesh. The Mind Workers struggled, but were quickly dragged down into the sea of slimy pink creatures and torn to pieces, oozing thick blue liquid, the Bacteria feeding off the liquid and squealing in delight while the Emotions looked on in horror.

In less than two seconds the trickle of Bacteria had become a flood and Phil gave up trying to contain it. He reached into himself and pulled out one of the purple blobs inside his body, slamming it down on the ground. The blob exploded on contact, splashing drops of purple liquid that quickly evaporated into a fine mist – the same purple gas the Emotions had seen earlier. Phil repeated his action three, four, five times – a giant cloud of purple mist enveloped the area and the screeches of dying Bacteria filled the air.

"Riley?" Mom's voice boomed again, reminding the Emotions that Riley was supposed to be on the phone with Mom right now.

"Don't worry about me!" Phil yelled loudly from the back of the room, over the din of more explosions and Bacteria screaming. "Just do your jobs! Backup is on the way!"

The Emotions turned uneasily back to their console and tried to remember what they had been doing before they'd been interrupted. Even Joy couldn't help glancing back nervously every few seconds, seeking reassurance that Phil and Mike were still standing strong, keeping the vicious Bacteria away from the console.

Hearing Mom's voice always made Riley feel a little better. Thus, Joy would have a temporary boost in control, but she knew she shouldn't be in complete control with Riley's sickness still a source of worry. She needed Fear to move with her.

Joy shouted across the console at Fear, snapping him out of staring fearfully at the battle behind them. "Fear, come on, we're talking to Mom!"

Fear startled and hurriedly turned to his console, starting to push buttons and forgetting to coordinate with the other Emotions. Joy let herself smile a tiny bit as she timed her own actions to synchronize.

"Mom," said Riley, "I'm sick and my head hurts really bad. What should I do?"

"Oh no, my poor baby! What happened?"

"I don't know. I don't know if I caught it from Meg or from – "

Disgust stopped Riley's voice with a panicked push of a button. "No, don't tell Mom about the party!" she hissed.

"uhh… it hurts…" Riley muttered.

"When did this start?" Mom asked, worried.

"Woke up with it this morning."

"Can you get to the campus health center?"

"The light makes it worse. I don't think I could even go outside."

"Is it bad?" Mom was even more worried now.

"Yes…"

"Why don't you call 911, honey. Better safe than sorry. Let's hope it isn't anything bad, but I want you to see a doctor right away. Call me when you get to the hospital, okay?"

"Okay, Mom… Love you."

"Love you too!"

Riley hung up.

"I knew it," Fear whined, "we're gonna die!"

"Fear!" Joy snapped, getting his attention. "One thing at a time. Let's call the ambulance, alright?" The truth was she snapped at him only because she was starting to worry for Riley's safety herself, and she'd taken it out on him. Joy made a mental note to apologize later once they'd sorted everything out.

The explosions and screams continued in the background, uncomfortably close behind them, as the Emotions worked together to get Riley talking to the 911 dispatcher, giving her dorm building and room number.

After getting off the phone, the Emotions turned around to see the entire rear half of the room blanketed in purple smoke. Phil and Mike had moved to a position between the console and the back half of the room, evidently having given up on trying to keep the Bacteria entirely out of Headquarters. Phil launched globule after globule of his purple gas into the endless waves of Bacteria, which seemed to charge forward like lemmings, heedless of the danger. Mike grabbed any stray Bacteria that managed to make it past Phil's purple wall of doom and gobbled them up. So far, they seemed to be holding back the onslaught.

Joy, being who she was, soon started skipping around like a cheerleader, shouting encouragements to the two White Blood Cells. Phil glanced back, laughed, and returned his attention to the battle.

But Fear couldn't help but notice that Phil had become noticeably paler and more transparent in the last couple of minutes. Much of Phil's purple shade had been coming from the globules of purple gas he carried inside him. But now, most of Phil's cytoplasm was empty, with only a few of the purple sacs left inside him.

Then, just as Fear feared, Phil reached deep inside himself and pulled out his last globe of purple. The last of his poison gas which had killed untold hundreds of the enemy.

"Shit! I'm out of ammo!"

As if on cue Joy stepped sideways and grabbed Fear's hand to give a reassuring squeeze, succeeding in somewhat quieting the meltdown she knew he was about to have.

But Mike only sighed wistfully. "I guess this is goodbye, then."

Phil nodded, shaking one of Mike's hands with one of his own. "A pleasure serving with you, Mike." Then he turned to the Emotions. "Joy, Fear, Anger, Disgust, Sadness. It's been my greatest honor knowing you!"

"Phil?" Joy asked in concern. She vaguely felt Sadness take her other hand, trying to comfort her, reminding her that she didn't need to fight the tears that were about to leak from her eyes. There was no Joy without Sadness, after all.

As the purple mist began to dissipate, more Bacteria could be seen crawling in through the large hole in the wall. They joined those crawling out from the pit, which had become a pond made of the black sludge of their comrades' deaths, and the sea of pink Bacteria advanced menacingly as they chewed up the ground in front of them.

"We all protect Riley in different ways," Phil said solemnly. "It's my job to die for Riley, just as it's your job to live for her."

Joy felt a tear slide down her cheek, and ignored it as she tried in vain to think of the appropriate thing to say to someone who was about to sacrifice himself for her. All she could come up with was the memory of Bing Bong's loss seven years prior; his _take her to the moon for me!_ echoing in her mind as she watched yet another savior in his last moments.

"That's so sad," said Sadness with her trademark feeling. "Why would they make you just to die?"

Joy heard Anger and Disgust sniffle in the background, as they both fought back tears as well. Sadness squeezed her hand lightly in reassurance and then let it drop, moving to comfort the others. Joy understood that Sadness knew she would be okay because of her experience in the memory dump seven years ago, whereas the other Emotions hadn't gone through the same thing and had more need at the moment. Sadness went, as always, where she was most needed.

"It's alright," Phil said, taking a quick glance at the oncoming Bacteria behind him. "Meeting you in person is already far more than I ever dreamed possible," his voice was that of an old man cracking from emotion, "If you see my niece or nephew, please tell them what happened."

Phil rolled forward, gobbling a few bacteria on his way until he was in the thick of it. Then, he opened his mouth and spit out silky strands of dark blue material as he spun around. The material seemed to be coming directly out of his nucleus, which rapidly shrank as he released torrents of dark blue that coated the mass of Bacteria emerging from under his location. Strands of blue silk flew all around him, sticking to the ground, to the walls, and to each other, forming a thick web.

The silk strands stuck to the Bacteria, too, like spider silk. Dozens upon dozens of Bacteria growled, howled, and screeched in anger as they found themselves stuck, trapped among the blue strands of Phil's final attack. And the strands burned, too, just like the poison gas. As the mass of Bacteria struggled within the net, they pulled the strands this way and that way, and each time a strand was pulled taut some of the Bacteria would get another painful burn line across their body. Although the Bacteria could bite down on individual silk strands, and chew through them, only those near the outside of the trap could hope to get out before becoming too injured. For the greater bulk of the pink invaders, it was death by a thousand cuts.

The scene was suddenly interrupted by a shrill voice from around the corner that was only partly covered by the dying screams of the Bacteria.

"Phil! Wait up, we're coming!"

The Emotions turned in surprise to see three more White Blood Cells rounding the corner. Each of them looked exactly like Phil did when they'd first met, except for slightly different "faces" embedded on their "front" surfaces. The new arrivals stopped short at the same sight that was drawing the Emotions' attention. Two of them gasped in wonder and exhilaration, but the third was distraught.

The core of the blue silk was Phil's very own DNA, released from his nucleus to become a final barrier against the invaders. Phil's nucleus vanished into nothing, and his face barely had time to look back and smile in satisfaction before fading into its empty cytoplasm, which then burst in a shower of clear liquid and vanished into the depths of the large silk tangle he'd created. With his final sacrifice he had ensured that hundreds of the enemy would go with him.

"Nooo! Uncle Phil!" This White Blood Cell cried out with the high-pitched voice of a child, revealing herself as the niece Phil had mentioned earlier. One of her companions reached out to console her. The Emotions, transfixed by the epic scene that had just unfolded, still reeling from the shock of so much up-close death and destruction in their own home, paid little attention.

Only when the other new White Blood Cell turned around to introduce himself did the Emotions snap back to reality. "Hi guys, sorry we're late." He extended his hand, and Joy numbly shook it. "I'm Philip, I'll be helping to protect you guys for a while, along with my friends here."

More by force of habit than anything else, Joy watched herself shake Philip's hand and heard her own voice say "Nice to meet you, I'm Joy" with only dim awareness that she was the one speaking. The other Emotions introduced themselves in similarly hollow fashion.

"Wait," Philip suddenly realized, "you're THE Joy? And you're Sadness, Disgust, Anger, Fear…" He turned around in excitement. "Hey Philippa, come over here! We're guarding the Emotions! This is so awesome!"

Philip's companion quickly looked up from her consoling of Phil's 'niece' and dragged the other White Blood Cell behind her. "Wow, this is such an amazing honor! Hi, I'm Philippa, pleasure to meet you!" To the Emotions she looked exactly the same as Philip and could only be distinguished by voice: "Philip" sounded like a polite and enthusiastic young man, while "Philippa" spoke with a female voice bearing much resemblance to that of Riley's mother.

The third White Blood Cell looked the same as the other two with only her girlish voice and mannerisms marking her as "younger" than her companions. "Hello, I'm Philia," she said shyly with a small wave.

The Emotions looked back and forth among the three similar-looking protectors awkwardly.

"Is it just me, or am I sensing a pattern here?" Disgust snarked.

"Oh, don't worry about telling us apart," the male-voiced White Blood Cell said flippantly. "We'll all be dead by tomorrow anyways." _Wait, what's his name?_

The child-voiced White Blood Cell instantly burst into tears, simultaneously with Fear starting to babble in terror and a moment later being silenced by Anger, who punched him out cold. But Anger could do nothing about the (to him) irritatingly emo White Blood Cell who was now rubbing her eyes and crying something like "I don't wanna die!" while ejecting "teardrops" of cytoplasm to both sides from the corners of her "eyes".

"Philip!" scolded the White Blood Cell with the woman's voice. _Oh, right, the guy's name is Philip…_ "Did you have to say that out loud!?" She then turned to her young companion, trying to soothe her, "Come on, baby, it'll be alright…"

"You can't protect her forever, Philippa," argued the scolded Philip. "We both saw how many germs we're dealing with here." _Okay, so the mom is Philippa and the little girl is… what's her name... they're all Phil-something…_

"She's only four hours old, for crying out loud!" Philippa snapped. "Let her have the last of her childhood, will you?"

The Emotions could only watch the exchange and grow more slack-jawed with every new revelation.

"Well, I'm going to the front," Philip declared, motioning to the huge writhing mass of immobilized Bacteria behind them, where a few of the Bacteria were beginning to individually chew and wriggle themselves free of the massive silk trap. Mike was crawling at top speed back and forth along the line, chasing down and eating each Bacteria as it emerged. "Send Philia over when she's 'grown up' enough." With those words Philip rolled away in a huff to join Mike in the pursuit of escaping Bacteria.

"You're only _four hours_ old," Joy said in disbelief, finally managing to string together the words to express what all the Emotions were thinking.

"Yes," Philia answered, nodding with her whole round body. Somehow, her mannerisms still managed to remind the Emotions of how Riley had once been as a child many years ago. They tried not to think about what Philip had said earlier about the White Blood Cell's impending death.

An alarm blaring from the console diverted the Emotions' attention back to their own jobs. Someone was calling Riley's name out in the real world, and there was the sound of pounding on the door.

"It's the ambulance people," Disgust announced. "We need to get Riley over to them!"

The Emotions ran for their seats at the console. Together, they all helped steer Riley out of bed, fighting off the sensation of nausea when they made her stand up, then grabbing Riley's phone and wallet before stumbling to answer the door.

Three synchronized lever pulls by Anger, Joy, and Fear maneuvered Riley's hand onto the doorknob and then a button push from Sadness and two levers by Disgust twisted the doorknob open. The viewscreen seemed to light up with the light of a thousand suns as the harsh fluorescent light of the corridor flooded into Riley's darkened dorm room, and as the Emotions shielded their eyes, so too did Riley.

Two paramedics were at the door with a stretcher. "Ms. Andersen, are you alright? We're here to take you to the hospital."

Joy and Sadness reached for the levers to make Riley respond, but just as they did they were startled by the sound of metal clanging and popping as a portion of the wall right under the viewscreen exploded inwards and a horde of greedy pink Bacteria burst into the room, right in front of the control panel, some of the little creatures landing only a short distance from the side of the control panel where Disgust was seated.

Naturally, all the Emotions were startled and panicked but none more so than Disgust, who shrieked and leaped up from her seat to put some distance between herself and the slimy pink critters. In her haste, she accidentally brushed a lever, which made Riley pitch forward and collapse into the arms of the paramedic. Whatever Joy and Sadness had planned to verbalize was promptly forgotten in the chaos.

To the paramedics it looked like Riley had just fainted. Fortunately, the uniformed man managed to catch her, and together with his colleague, lifted Riley into the stretcher. "Ms. Andersen! Are you okay?"

The Emotions saw and heard, but hesitated to respond since that meant approaching the Bacteria. Meanwhile, the two White Blood Cells from earlier had rushed over. "Too many to eat, throw a grenade!" they heard Philippa's voice calling out. A few explosions of purple mist later, the Bacteria had been contained, the ground between the control panel and the viewscreen was covered in patches of steaming black sludge, and the two White Blood Cells were sitting at the hole in the front wall, taking turns seizing each Bacteria that came through.

"Philia, go switch places with Mike," said Philippa. "We need him over here to clean up the mess." The younger cell obediently rolled away, skirting the edge of the muck.

At last, the Emotions were back in control at their panel and opened Riley's eyes to see the ceiling lights rushing by high above – and feel the pain shooting from Riley's eyes right into her brain, causing them to quickly close her eyelids again. But they'd figured out where Riley was – she must be on the stretcher, being wheeled down the hall to the ambulance.

"Where are we going?" Riley asked out loud.

"University Medical Center," answered one of the paramedics. "We'll take care of you, everything's going to be alright, ok?"

Riley lay on the stretcher with her eyes closed and tried not to move. This required little active attention from the Emotions, who turned to examine the battles going on at both the front and the back of Headquarters.

In the rear of the room Philip and Philia were rolling around and pouncing on Bacteria. They had things under control, but their front line was also uncomfortably close to the core memory holder in the center of the room – they would not have much room to retreat if anything happened.

At the front, Philippa and Mike had the breach walled off between them and the Bacteria were simply continuing to waltz in to their immediate deaths.

"Hey guys! Need any help?"

The new arrival was another White Blood Cell who, to the Emotions, looked identical to the last three they'd seen. Fortunately, his voice, that of a young boy, was different enough from the others to mitigate any confusion.

"Hi Philby!" said Philia, obviously recognizing a friend's voice.

"Glad you could make it, Philby!" Philip called out. "Why don't you go give Mike a break?"

Philby, the smaller round White Blood Cell, dutifully switched places with Mike, the giant cylindrical White Blood Cell. Mike lumbered over to the middle of the room and melted onto his feet with a tired sigh. The Emotions watched all these events with fascination.

"How do you guys all know each other's names?" Joy asked what all the Emotions wanted to know.

"Honestly, I'm just as mixed up as you are," said Mike. "Phil and his guys all know each other from before, but I only just met them today when they got here."

"Then how do they know who you are?"

"Because there's only one of me here right now," Mike replied as if it made perfect sense, even though to the Emotions it didn't. "If there was more than one of me then they'd be mixed up too, I reckon."

The confused Emotions fell silent for a bit.

"How do you guys, you know… work? No offense," Joy added quickly, "it's just, well, the only cells we've ever seen around here are Mind Workers, and we had no idea we had a security guard up on our roof all this time. Not that we're complaining, it's great having you here to, um, protect us from those things!"

"Well," said Mike, "where do I begin… How much do you know about our Immune System?"

"Riley learned about that in school, didn't she? You guys are all White Blood Cells, and you eat the Bacteria."

"That's right."

"Well, not all White Blood Cells are the same. I'm a Macrophage, which means I have an assigned area, and I eat whatever Riley's other cells don't need anymore. The brain doesn't make a lot of junk, so I spend most of my time asleep, waiting for the smell of trouble to wake me up. The other guys are Neutrophils, they patrol all through Riley's body and hunt Bacteria wherever they might appear. Then it's my job to clean up the mess when they finish. We also have Lymphocytes, you probably haven't met any yet. They're the virus killers, because they can see Viruses hidden inside cells where the rest of us don't see them."

Some indistinct shouting came from the back of the room. The screeches increased in volume and a few explosions followed. The Emotions looked back to see two more breaches in the wall and more Bacteria piling in, clambering over the huge blue mass of silk deathtrap that covered the floor. Philip and Philia were throwing their gas grenades and killing off the new arrivals by the dozen.

"I better go see if they need some help," Mike said. He popped out rows of stubby little feet under him and began crawling to the action. "I've had enough gunk for a lifetime today," the Emotions heard him muttering to himself, "sure hope my replacement comes soon…"

"Wait!" Fear said, "Are you sure you can hold them off? Isn't there some way we can get more help?"

The console alarm beeped again, barely audible over the sounds of chaos from the back of Headquarters. But even if the Emotions had missed the alarm, they couldn't have missed the sudden swaying of the room around them. All of them wobbled unsteadily as Headquarters itself seemed to shake from the bottom up – something was physically moving them from the outside. "Ms. Andersen!" A strong male voice boomed through the speakers, just audible over the loud screeching of a hundred Bacteria in their death throes. "Ms. Andersen, wake up!"

The Emotions got back to the console and made Riley open her eyes to see who was talking to her now, gritting their teeth through the pain. It was a stout young man in a white coat over a shirt and tie. "Ms. Andersen," he was saying loudly while shaking Riley awake by her shoulders. "I'm Dr. Johnson. I'll be taking care of you today."

"Oh, good, it's the doctor!" said Joy. "We've arrived at the hospital!"

Fear, Disgust, Joy, and Sadness all pushed various buttons.

"Hi, Dr. Johnson," said Riley weakly.

"It looks like you're having some pain," said Dr. Johnson. "We're here to help. We just need you to tell us a little about how this started."

"I woke up this morning and my head hurt…"

"Can you point to where the pain is in your head?"

Riley made a motion indicating all around her head.

"Is the light bothering you?"

"Yes…"

"I'm sorry to hear that. We'll turn down the lights as soon as we're done here, okay? I just need to…"

The Emotions didn't hear what the doctor said next as suddenly a chunk of the roof fell right in front of the console and a stream of Bacteria started falling from the sky, drawing everyone's attention. "Ack!" Philippa yelled in surprise and rushed to stand between the console and the Bacteria. One of the slimy pink creatures plopped right onto the console and stared Fear right in the face! "AHHH!" Fear scrambled away from the console, the others also backed away slowly.

For Riley all these events manifested as simply another wave of pain and nausea, which distracted her from what the doctor was saying. The doctor placed his stethoscope on her chest.

"Take a deep breath," the doctor said loudly, his voice echoing through the speakers in Headquarters. But the Emotions were staring at what were now three scary gremlins occupying their console.

"Get those things off the console!" Disgust screamed.

Philippa oozed and clambered her way onto the console, still ejecting clouds of purple vapor from her body sideways towards the Bacteria raining down from above as she rolled along the console and grabbed for the Bacteria sitting on the buttons. The Bacteria wriggled and fought to escape, and one of them popped out of Philippa's hands and flew towards the Emotions. Joy yelped and Sadness squealed as they both jumped back just in time to avoid the Bacteria which landed right where they had been standing a moment ago. "Oops!" Philippa yelled, "sorry about that!"

"Where's your backup!?" demanded Anger, as he kicked the Bacteria as far away as possible.

The doctor's voice was blaring from the speakers, "Ms. Andersen! Can you hear me? Open your eyes if you can hear me!" but the Emotions had no way to answer, and Riley lay unresponsive on the emergency room stretcher.

"Reinforcements are coming," Philippa said, "we just don't know when!"

"We can't hold this position much longer!" Philip yelled from across the room. "We need to evacuate!"

The Emotions looked back and saw the two White Blood Cells retreating as they filled the back of the room with purple vapor. Their bodies were now mostly clear white, having depleted most of their ammunition supplies against the Bacteria. One White Blood Cell backed up to either side of the core memory holder in the center of the room as they gradually retreated…

"No, wait!" Joy shouted, as the Emotions ran towards the back of the room. "The core memories! We have to save them!"

"What?" Philip asked, loudly to make himself heard over the chaos, but still confused.

"Those colored orbs you're standing next to," Joy explained. "Don't let the Bacteria get to them!"

The longest ten seconds of Joy's existence followed as she and her fellow Emotions ran to the core memory pillar and began unloading the precious core memory globes, fifteen in all. Philip and Philia, the White Blood Cells, covered them with a huge burst of purple explosions, using up almost all their remaining gas to advance a few steps forward and clear enough space for the Emotions. Mike had moved to help out at the front of the room and had not had enough time to clean up the oily black sludge on the ground, and although Philip and Philia had rolled forward through it without trouble, the Emotions all looked distinctly uncomfortable as they worked around the core memories, the sludge squelching under their feet and oozing between their toes. Fear hyperventilated into his paper bag as he held three memories in his long fingers. Disgust looked ready to throw up as she clutched her three memories in her arms, but refused to hand them off, determined to do her part.

The five Emotions now stood in a circle, each carrying three of Riley's core memories, trapped in the center of Headquarters by a sea of Bacteria. The White Blood Cells had withdrawn to form a protective circle around them.

"Okay, guys. What's the best way out of here?" Philip asked.

"I think we can hide out in Long Term Memory for now," Sadness offered.

"It's that way," Joy said, pointing towards the back of the room. What remained of Phil's giant blue silk trap was now entirely invisible, covered up by the sea of Bacteria crawling over it and towards them. The exit leading to the Train of Thought platform was completely infested.

"Who's got ammo left?" Philip asked his companions.

"I have some," Philia motioned to herself, though the Emotions could see that only a few purple globules were still floating around at the bottom of her cytoplasmic body.

"Only a few left," Philby said.

"I'm out," Philippa said.

Philia sniffled at that, as if trying not to cry. Recognizing her own emotion, Sadness offered a hand, which Philia gratefully took up in one of her own gelatinous hands.

"It's alright," Philippa consoled. The Emotions still wondered why she seemed happy about their predicament and not the least bit worried.

"How can you say that!?" Anger protested. "Are you all crazy?"

"We're crazy for you," Philippa said, winking at her own joke. The Emotions did not seem particularly comforted.

"We're Neutrophils," Philip explained. "We weren't going to live more than a couple days either way, really. They make us by the million down in the great marrow factory and nine hundred ninety-nine thousand of us just grow old and die without ever seeing much action."

"Those before us were lucky to get ten or twenty kills in a lifetime," Philippa added. "It's every Neutrophil's dream to die in battle, surrounded by the crumbs of our enemies, putting every grenade we were born with to full use. Getting to do it while defending Headquarters is just icing on the cake!"

"Okay," Philip said, "it's time… We'll clear the path, you stay safe until it's all over!"

Philip charged forward through the sea of Bacteria, squishing them out of his path and creating a temporary clearing in his wake. And then, in one gargantuan burst, Philip seemed to explode before their eyes into a massive cloud of blue silk, which only momentarily floated (though it felt like eternity to the Emotions looking on) before gradually settling down to the ground, coating the Bacteria to either side and trapping them out of the way. The trapped Bacteria wriggled under the confining blue strands, creating a very unappetizing effect of moving landscapes.

"Come on!" Philippa yelled, leading the Emotions through the writhing furrow of stuff towards the large hole in the wall which led to the train platform. She halted and glanced back upon hearing Joy shout behind her.

"Mike, come on!" Joy was looking back in concern at the massive worm-like White Blood Cell, who seemed to be huffing and puffing as he straggled behind the rest of the group, the Bacteria flowing around him like water on the floor.

"Go on ahead, I'll be fine!" Mike shouted back. Despite his apparent exhaustion, he was still actively grabbing the pink critters all around him and eating for all he was worth. The Bacteria were as vigorous as ever in trying to wheedle their way out of his grasp, but there were so many of them that Mike wasn't running out of prey anytime soon.

"He'll be okay," Philippa assured them. "I'll clean out this train station now. It's been a supreme honor - and I love you all!"

"Love you, Mom!" Philia shouted back from the rear of the group. She sounded emotional, but far less distraught than she had been before.

Philippa was gone by the time they turned the corner and burst into the train station. The Emotions found the Train of Thought parked neatly in the middle of the station – but it was covered in blue webbing with mounds of screaming Bacteria filling the train cars, wedged in between the gaps, trying to fight their way out. They ran up to the engine at the front, but the driver's compartment was blocked off, and through the front window they could see a mass of angry Bacteria trapped inside the locomotive, pushing on the windshield and growling.

"Hey, where's the driver?"

"I think he got eaten…"

"Well, just great, how are we going to get across now?"

"We'll have to walk on the rails."

However optimistic Joy sounded as she said that, everyone knew she really wasn't.

"Don't worry," Philby said brightly, "We can stick to the rails and carry you guys inside us."

"Yeah, we can be your hamster balls," Philia added.

"I'll walk, thank you," Disgust answered. "No offense," she added hastily. The other Emotions nodded in agreement.

The Emotions walked down the platform, occasionally shaking off strands of the blue silky material that Philippa had left behind on the ground, which was now also coated with black tar residue from the dead or dying Bacteria underneath. At the end of the platform they carefully climbed down onto the rails, followed by their three remaining White Blood Cell escorts.

They emerged into the atmosphere outside Headquarters and stopped in wonder.

They were standing on the railway high above the Memory Dump, with a panoramic view of all the distant reaches of Riley's mind. But the Memory Dump was not the huge black canyon they were accustomed to.

It was full to the brim with a huge mass of pink Bacteria that were spilling out onto the banks of Long Term Memory and engulfing the lower levels of several of the Islands of Personality. The Emotions could see the pink dots in many of the corridors between the shelves of memories. Blue patches floated around on the sea of pink, the traps ineffective as they simply didn't reach anything solid.

Dozens of White Blood Cells, all identical to Phil and his fellow Neutrophils, were floating among the tide of pink creatures, in various stages of stuffing handfuls of Bacteria into their mouths, launching purple grenades, and/or exploding themselves into blue silk traps. Clouds of purple gas went off like geysers all over the landscape; some really did look like they were coming from deep under the canyon full of Bacteria. Every so often, a series of purple eruptions was followed by a much bigger blue eruption, signifying the heroic sacrifice of yet another White Blood Cell.

"Wow, what a magnificent view, isn't it?"

Everyone looked up towards where the new voice had come from. It was another worm-like White Blood Cell, evidently of the same species as Mike – he was crawling down the exterior wall of Headquarters' broken dome, over a thick layer of the same blue silk stuff the Emotions had become intimately familiar with in the last few hours.

"Oh, finally!" Mike sighed in relief. "Are you here to take over for me?"

"That's right!" said the other cell. "Hi guys, I'm Mack! And this is my partner Marco," as he said this, another White Blood Cell oozed down the wall and pulled up alongside him, giving a friendly wave to the group assembled below them on the train tracks.

"I feel so sick after eating all that toxic gunk," Mike moaned. "I don't think I can walk much farther…"

"Thanks for doing your part to keep this place clean, then," Joy said. "Will you be okay?"

"I'm afraid not," Mike replied, sounding slightly out of breath. "A Macrophage can only eat so much before his own insides turn into into the very junk he's meant to eliminate. Whether it takes six months or six days, once he can no longer digest any more waste, it is the duty of his successors to digest him, just as they in turn must be digested by those after them…"

As diverse as the Emotions were, all of them shared the feeling embodied by their blue teardrop-shaped member as they began to realize that not one of their new friends that day would be making it to the end with them.

"Now, my time has come, and I am most saddened that I will be unable to continue on the rest of your journey. But I know that my successors will serve just as excellently as I have, and it has been my greatest pleasure and honor to serve as your resident Headquarters guard."

Mike stretched his arms out and embraced all the Emotions in a group hug.

"Goodbye, Mike," whispered Joy.

The outlines of Mike's face faded into the front of his body, his arms retracted, his blue nucleus core split into fragments and dissolved, and his entire cylindrical body seemed to melt like melting ice cream onto the train tracks. Some of it was dripping from between the tracks down into the chaos far below.

The other two Macrophages, Mack and Marco, had come forward unnoticed, but then they began slurping up the liquefied remains of Mike's body, creating a bit of noise despite trying to be quiet. The Emotions looked on awkwardly, knowing that this was how things were "supposed" to go and thus hesitant to ask them to stop, yet still feeling uneasy at the sight of their late friend's remains being "cleaned up" in this manner.

"Go on," said one of the Macrophages. "We'll catch up!"

The Emotions turned away with mixed feelings, though not before catching the tune the two Macrophages were humming as they continued eating their deceased comrade, a tune that sounded like the opening to _that one old Disney movie, what was it, Lion King?_

The group continued on down the train tracks; further ahead, the tracks were invisible as usual, with only the portions near them visible, and more being revealed as they took each step forward.

But the train tracks were swaying from side to side, and seemed to be getting more unstable as they went further towards the middle of the chasm. And they were descending towards the land on the other side – right into the Bacteria emerging from the Memory Dump.

Rolling on ahead of the Emotions, Philby pointed this fact out. "We're gonna have to fight our way through them when we get across," he said.

Out in the real world...

Dr. Johnson frowned at his suddenly unconscious patient, the worry evident in his youthful face. After listening to Riley's quiet breaths and heartbeat for a few seconds, he turned and quickly strode out of the room, finding the nurse. "Hey, can you start an IV line on the young lady in room 10? A liter of saline, and a gram of vancomycin and two grams ceftriaxone, stat please."

"You don't mean room 9?" the nurse asked. "I just did all that on her."

"No, that's right. I think both of them have the same thing."

"Oh, okay."

* * *

 _Scientific notes:_

 _Riley's Illness - Most of the characters have no medical background, so they don't know this, but her symptoms are typical of meningitis: headache, nausea, light sensitivity, and neck stiffness (nuchal rigidity). This is a VERY common sickness in college dorms and can be caused by various bacteria - in this case,_ _Neisseria meningitidis. There is a meningococcal vaccine that prevents 4 of the 5 major subtypes of N. meningitidis - however, no vaccine has yet worked against_ _serogroup B, which is presumably the type involved in our story. The current treatment for all types of bacterial meningitis (both N. meningitidis and Streptococcus pneumoniae) is IV antibiotics given as soon as possible._

 _These bacteria get around using pili and flagella - their many noodly appendages. Macrophages and neutrophils such as Mike and Phil have a hard time capturing and phagocytosing these bacteria because of their slippery polysaccharide capsule (outer coating). Species in the Neisseria genus of bacteria include N. meningitidis (causes meningitis) and N. gonorrhoeae (causes gonorrhea). I show them as pink because they are Gram-negative, although in reality all bacteria are colorless unless a stain is applied in the lab to make them visible under a microscope._

 _Mind Workers - I interpret the Mind Workers as glial cells - support cells that help the neurons (Emotions) function in their "decision-making" capacity. There are about 20x more glial cells than neurons in the brain. The most common of these are astrocytes, whose functions include repairing damaged areas of the brain (filling them in with scar tissue - e.g. construction workers) and maintaining the blood-brain barrier (e.g. the security guards seen in the movie). The train conductor Mind Workers might represent oligodendrocytes - the glial cells that help impulses flow through neurons by providing electrical insulation to the wire-like axons that carry neuron signals. The Emotions themselves are not individual cells, but rather abstract representations generated by the firing of many neurons throughout the brain._

 _Macrophages - Mike describes himself as a Macrophage: he is actually the brain's specialized version of a macrophage - a microglial cell. Under a microscope, most macrophages look like round or shapeless blobs, but the microglia of the brain are special - they're shaped like narrow cylindrical structures. Macrophages primarily eat dead/dying tissue, but are also capable of eating bacteria (phagocytosis)._

Macrophages try to digest everything they take i _n, but sometimes a couple molecules here and there get missed, and they accumulate in the macrophage over time. When a macrophage wears out, like other worn-out cells, it commits suicide by a process called apoptosis, in which the cell nucleus fragments and proteins which maintain the outer 3-D shape of the cell are digested. Without those proteins, the whole cell becomes mush and is ready to be cleaned up by the next macrophage._

 _Neutrophils - Phil et al are Neutrophils, the major anti-bacterial white blood cell in humans. Neutrophils, unlike macrophages, carry a large arsenal of "granules" containing various proteins and chemicals that poison bacteria and digest/liquefy human tissue. This creates the white stuff called pus. Neutrophils kill bacteria in 3 ways: 1) phagocytose and digest bacteria; 2) release their payload of toxic stuff; 3) release their nuclear DNA to create barriers that entrap bacteria. This last method results in the death of the cell since the DNA is the physical "instructions" for keeping the cell alive._

 _Under the microscope, all cells are colorless unless a stain is applied beforehand. The stains used to visualize blood cells are Hematoxylin and Eosin (H &E). DNA stains blue, which is why cell nuclei are often pictured as blue dots on a microscope slide._


End file.
